This invention relates to agricultural balers and, more particularly, to such balers provided with mechanisms for controlling the length of bales being formed.
For many years, balers providing rectangular bales of crop material have been fitted with mechanisms for controlling the length of the bales being formed. Bales of the required length are being tied and then discharged from the machine. However, the accuracy of known bale length control mechanisms has been found lacking which until more recently has not been a particularly serious matter. With the advent of specialist equipment for handling bales, however, it has become necessary to control the length of bales more accurately because any significant variation may adversely affect the ability of the equipment to handle and/or transport the bales.
The variation in the length of a bale arises from the fact that a plunger is reciprocable within a bale case or chamber to compress individual wads of crop material, fed from a feed chamber, into an integral bale. When the bale length control mechanism is operated, the completed bale is tied in the time it takes for the plunger to undergo a full stroke so that, if the length control mechanism is operated late or early, then either one more or one less plunger stroke will take place, whereby the length of the bale will be greater or less by one wad of crop material usually of the order of 10 cms. Clearly, the length control mechanism could malfunction to the extent of allowing more than one extra or less plunger strokes but normally the discrepancy in length is due only to one extra stroke. This is because the length control mechanism is usually in the form of a trip mechanism and the latter often "hangs up" at the point of tripping, thus allowing the baler plunger to undergo a further stroke and thus add an extra wad of crop material to the otherwise completed bale.
Typically, the trip mechanism comprises a trip arm in the form of a sector member provided with a track (often toothed) which is cooperable with, and driven by, a rotary member (often a toothed wheel) which, in turn, is driven by a star wheel which extends into the bale chamber and is rotated by the bales being formed as they progress along the bale chamber.